An arrangement in which a dipole sound source distribution is determined by setting a predetermined finite computational domain as a range for which a velocity vector in a flow field is calculated by particle image velocimetry (PIV: Particle Image Velocimetry), replacing the influence of a vortex outside this computational domain by the influence of a vortex within the domain, and then using an equation obtained by combining Howe's equation and a compact Green's function adapted to an object's shape, is known from Patent Document 1 below.
Furthermore, an arrangement in which a velocity vector of a flow field is computed by particle image velocimetry based on an image taken of a site to be measured, a sound pressure of the site to be measured is measured by a microphone, and a sound source distribution map is computed by cross-correlation calculation between the velocity vector and the sound pressure, is known from Patent Document 2 below.